1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to a one-chip vitality measuring image sensor for acquiring visible and IR images.
2. Description of the Related Art
Near-IR light is greatly reflected on leaves of plants, grasses, or the like. By comparing a Near-IR image with a visible image shown in FIG. 1, a vitality of a plant can be measured. A wavelength of the Near-IR light is in a range of 700 to 900 nanometers. The vitality of plant measured from these images can be used as an indicator for identifying a state of growth of the plant. In addition, the vitality can be used as an indicator for measuring a degree of freshness of plant for sale.
There is a method of acquiring the visible image and the Near-IR image, where a beam splitter, a visible image sensor, and an IR image sensor are used.
FIG. 2 is a view for explaining a conventional method using an image sensor. Referring to FIG. 2, light 10 including visible light and IR light is incident on a lens 21. The light 10 through the lens 21 is split by a beam splitter 22 to be transmitted to an IR cutoff filter 23 and an IR pass filter 25. The IR cutoff filter 23 filters the IR light from the light 10 and transmits the visible beam to a first sensor 24. The IR pass filter 25 passes only the IR light of the light 10 and transmits the IR light to a second sensor 26. The first sensor 24 is a visible image sensor which outputs the visible image. The second sensor 26 is an IR image sensor which outputs the IR image.
The visible and near-IR images acquired by the first and second sensors 24 and 26 are processed by an image signal processor (ISP). Before the images are processed by the ISP, the visible and near-IR images are temporarily stored in a frame buffer.
In the method of acquiring the visible and near-IR images, the optical filters including the IR cutoff filter 23 and the IR pass filter 25 are not easy to manipulate, and complicated operations for identifying the same points on several images are required. In addition, since complicated frame buffer and optics are needed, the cost is increased.